Plural GaN power devices such as Heterostructure Field Effect Transistors (HFETs) and Schottky diodes can be monolithically integrated.
FIG. 1 illustrates a conventional semiconductor circuit. Referring to FIG. 1, the semi-conductor circuit includes an inductor L1, a HFET Q, a Schottky diode D1, and a capacitor C1. A resistor R1, representing the output load, is also shown.
FIG. 2 is a graph showing current-voltage characteristics of the Schottky diode D1 illustrated in FIG. 1. In FIG. 2, a horizontal axis denotes a forward voltage of the Schottky diode D1, and a vertical axis denotes a forward current of the Schottky diode D1.
The semiconductor circuit of FIG. 1 is embodied as a sort of boost converter circuit. Referring to FIG. 1, the HFET Q is turned on in response to a bias voltage BV1 applied to a gate thereof. When an input voltage VI is applied via the inductor L1 in a state in which the HFET Q is turned on, a voltage drop between an anode of the Schottky diode D1 and a reference potential may be approximately 1 V and an output voltage VO may be approximately 400 V. In this case, the cathode of the Schottky diode D1 has a greater voltage than that of the anode thereof and thus the Schottky diode D1 is turned off due to a reverse bias. When the HFET Q is turned off, however, the voltage drop between an anode of the Schottky diode D1 and a reference potential is greater than the output voltage VO and thus the Schottky diode D1 is turned on. As such, the semiconductor circuit of FIG. 1 can boost the input voltage VI to a desired level of output voltage VO.
When the HFET Q is turned off and the Schottky diode D1 is turned on, a back-gate phenomenon whereby a drift layer (or a channel layer) of the Schottky diode D1 is partially depleted due to an electric field caused by a difference in potential between the drift layer of the Schottky diode D1 and a substrate (not shown) occurs. Due to the back-gate phenomenon, as illustrated in FIG. 2, the resistance of the Schottky diode D1 exceeds a normal value (plot 10) and increases in the direction indicated by an arrow (plot 20).